January 3, 2014 – Xianming Chen
Happy New Year! As we are heading into 2014, you may be wondering how bad stripe rust is going to be in the coming season. The good news is that stripe rust will likely not be bad for winter crop.
The current forecast for highly susceptible varieties to have 22% yield loss, in the low end of moderate epidemic range (20-40% yield loss) in contrast to low (<20%), severe (40-60%), and extreme severe (>60%) epidemics. This forecast is based on the December temperatures used in the first of our six models, and is the lowest level of forecasted stripe rust epidemics since we started using the new models in 2009. The low forecast level is due to the unusually cold spell of December 3-9. Forecasts will be made with other models as the season is progressing.
Regarding how good the forecast could be, we may use the last year as an example. In 2013, we forecasted yield loss of highly susceptible winter wheat varieties first as 41% on January 2 and later corrected to 37% using the first model based on the December temperatures. The highest yield loss was determined as 38% in the variety yield loss experiment and 42% in the fungicide testing experiment.
On November 11, we were checking winter wheat fields along Highway 26, Horse Heaven Hills, and the Connell and Ritzville areas, but did not find any stripe rust. We were told that stripe rust was found on volunteer wheat plants near Connell (Franklin Co.). Three days later, we received a report of heaven stripe rust infection in an ‘Eltan’ wheat field planted in the end of July near the Coulee City (Grant Co.) (Figure 1). The heavy stripe rust was due to the too early planting and the high precipitation in September. The cold spell in the early December should kill much of the rust in the field and surrounding areas. We will check the areas to see if the rust will survive. The next forecast will be made in early March.